Broadly, this invention is directed to apparatus which can be used to monitor the depth of granular material in a container or on a carrier.
More specifically, the invention is directed to apparatus which includes a unique probe tip fastened to complementary apparatus and electrically connected to electronic equipment whereby the depth of electrically conductive granular material, such as iron ore or sinter mix in a container or on a carrier, such as a sinter strand can be monitored, and which can also be used to control the rate of feed of the granular material.
Many devices have been used to determine the level of a fluid or a fluid-like granular material in a container. One such device used to indicate the level of a liquid in a container is an electrically conductive rod in series with a source of electrical energy, an indicating scale and a switch. The rod is connected to ground through the liquid and the wall of the container. The electrical resistance of the circuit is altered by the raising and falling of the liquid and the alteration of the liquid level is read on the indicating scale. As the surface area contacted by the liquid increases the resistance decreases and is shown on the indicating scale. A shoe or enlarged portion of a conductive body may be attached to the bottom of the rod to insure quick and sure contact between the rod and liquid when the rod is immersed in the liquid.
Another device used to measure the level of granular material in a hopper is comprised of electrically conductive material, such as carbon granules which are sensitive to a change in electrically conductive characteristics caused by pressure changes, enclosed in a flexible electrically insulating material, such as a tube of rubber. The device is mounted along one wall of the container. The ends of the device are connected to a bridge circuit by means of electrodes at either end of the tube. The change in pressure on the column of carbon granules by the change in height of the granular material in the hopper caused the resistivity of the carbon granules to change. The change is registered in the bridge circuit. By balancing the bridge to account for the change in the circuit, the height of the granular material can be found directly.
It has been suggested to monitor the position of a sinter mix pile on a sinter strand with a device as described in U.S. Pat. No. 3,155,277 issued to D. W. Fath et al entitled "Material Handling Control System." The device is comprised of a plurality of metallic electrical contacts positioned at predetermined intervals or distances from the sinter strand and parallel to the sinter mix pile. Since the contacts are at various distances from the pile not all the contacts are embedded in the pile at one time. When the pile touches a metallic contact, a signal of constant magnitude is generated. Hence, the position of the pile is determined only by the contacts which become embedded in the pile. The device has several serious drawbacks, namely the device depends upon a plurality of electrical contacts; the measurement of the pile is non-continuous and the accuracy of the measurement is questionable because od dust, dirt and grime which can accumulate on the contacts. The device is expensive to install and difficult to maintain. There is, therefore, a need for a simple, inexpensive, easily maintained device which can be used to obtain maximum efficiency of a sintering process.
It is an object of this invention to provide a device or apparatus including a probe tip fastened to complementary apparatus, which probe tip is electrically conductive and is characterized by having high electrical resistivity, the probe tip being electrically connected to electronic equipment whereby the depth of granular material in a container or on a carrier can be monitored and the feed of the granular material can be regulated.